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ChangeLog

0.5.0

In this release, we add some APIs to enable users to control more properties of devices, connections and the async-rdma background framework.

We tested async-rdma on some hardware RDMA devices(only Soft-RoCE before), and found that the default configuration cannot meet all hardware requirements. Some hardware needs special configuration, so we have added richer set interfaces.

We provide support for listening IBV async events. When the IBV async event occurs, it will be recorded. We will add more functions besides recording in the future.

New features

  • Add IbvEventListener to monitor ibv async events. Rename the original event_xxx.rs to cq_event_xxx.rs to distinguish cq event from ibv event.
  • Add manual cq polling trigger. Add PollingTrigger trait to enable multiple implementations of trigger. Implement channel based manual polling trigger and add related APIs.
  • Add API set_cc_evnet_timeout. To set the timeout value for event listener to wait for the notification of completion channel.
  • Add API to set imm flag in wc. The value of immediate data flag may be different on rdma devices. Users can change this flag by this API to adapt their devices.
  • Add experimental feature and recv with fn APIs.
  • Add set APIs for attributes of queue pair.
  • Add APIs to get the state of qp.
  • Add atomic_cas API and tests.
  • Add ibv_connect API for RdmaBuilder and Rdma. pub use Gid for ibv_conenct. You can connect to remote end by raw qp info no matter how you get it.
  • Enable users to create RemoteMr manually.

Optimizations and refactors

  • Increase default cq size. The cq may be full before next polling if the cq size is too little.
  • Add qp init attributes check.
  • Add cq_size and max_poll_cqe check.
  • Adapt new cm_connect API logic.
  • Replace self with &self in ibv_connect. Make it easier to use without the need of clone.
  • Refactor attributes structs of qp. Implement builder pattern for attributes structs by derive Builder. to reduce hand write codes and make the structs clearer.

Bug fixes

  • Replace assertion with debug msg. The length of mr is not always equal to wc.byte_len.

0.4.0

In this release, we add some APIs to make it easier to establish connections and provide more configurable options.

We provide support for sending/receiving raw data and allocating raw memory region to enable users to implement the upper layer protocol or memory pool by themselves.

APIs for supporting multi-connection can be used to easily establish multiple connections with more than one remote end and reuse resources.

New features

  • Adapt RDMA CM APIs. Add cm_connect to establish connection with CM Server. Add {send/recv}_raw APIs to send/recv raw data without the help of agent.
  • Add APIs to set attributes of queue pair like set_max_{send/recv}_{sge/wr}.
  • Add APIs for RdmaBuilder to establish connections conveniently.
  • Add APIs to alloc raw mr. Sometimes users want to setup memory pool by themselves instead of using Jemalloc to manage mrs. So we define two strategies.
  • Add APIs to alloc mrs with different accesses and protection domains from Jemalloc. MrAllocator will create a new arena when we alloc mr with not the default access and pd.
  • Add access API for mrs to query access.
  • Support multi-connection APIs. Add APIs for Rdma to create a new Rdma that has the same mr_allocator and event_listener as parent.
  • Add RemoteMr access control. Add set_max_rmr_access API to set the maximum permission on RemoteMr that the remote end can request.

Optimizations and refactors

  • Use submodule to setup CI environment.
  • Reorganize some attributes to avoid too many arguments.
  • Update examples. Replace unsafe blocks and add more comments. Show more APIs.

Bug fixes

  • Disable tcache of Jemalloc as default. tcache is a feature of Jemalloc to speed up memory allocation. However Jemalloc may alloc MR with wrong arena_index from tcache when we create more than one Jemalloc enabled mr_allocators. So we disable tcache by default.

0.3.0

In this release, we adapted Jemalloc to manage RDMA memory region to improve memory allocation efficiency.

Some safety and performance issues have been fixed, thanks to @Nugine's comments.

New features

  • Jemalloc was adapted to manage memory region. We inject custom extent hooks into Jemalloc to empower it to manage RawMrs. That avoids the overhead of repeatedly reg/dereg memory region. Use BTreeMap to record the relationship between addr and RawMr. When we alloc memory from Jemalloc, mr_allocator will lookup the related RawMr by addr.
  • Add timeout mechanism for RemoteMr. Request RemoteMr from remote without timeout may cause remote OOM. So we add RemoteMrManager to manage RemoteMr and free them after timeout.

Optimizations and refactors

  • Avoid unnecessary overflow checking operations to improve performance.
  • Optimize cq poll work flow. Poll single CQE at a time is inefficient in high concurrency. Here we made the maximum number of CQE to poll at a time configurable. Accordingly, event_listener should be able to wake up multiple tasks at a time.
  • Redesign LocalMr and event_listener to ensure cancel safety. Let event_listener holds the Arcs of the LocalMrInners that are being used by RDMA ops to ensure cancel safety. LocalMr was replaced with new struct LocalMrInner. Because every struct that can use APIs should hold an Arc of the mr's metadata, but previous LocalMr can't hold itself. Add RwLock to avoid potential race condition.
  • Add zeroed LocalMr API. Uninitialized memory region is fast but not safe, so we add zeroed API and mark uninitialized memory alloc API as unsafe.

Bug fixes

  • Fix Gid impl that used to have alignment mismatch bug.
  • Fix the handling of return values of ibv APIs. Most ibv APIs return -1 or NULL on error and if the call fails, errno will be set to indicate the reason for the failure.But there are some places treat the return value as errno, we fixed these wrong handlings.
  • Ensure cancel safety. Undefined behavior will happen if the future dropped(cancelled) during the execution of RDMA operations. So we redesign LocalMr and event_listener to hold Arc of memory regions until the operations are complete.
  • Mark unsafe traits and functions. The safety of access traits and functions cannot be guaranteed by themselves. So we need to mark them as unsafe. And the unsafe traits are marked as sealed to avoid being unsafely impl externally.

0.2.0

In this release, the code related to memory region has been reorganized. This change makes the abstraction more explicit and easy to maintain later.

Some new APIs for RDMA operations with immediate data was added. And we also fixed some bugs, which made the lib more stable.

New features

  • Implement memory region slice. LocalMrSlice and RemoteMrSlice enable us to operate on part of memory region. And we can only get one mutable slice or many unmutable slices at the same time, just like any other type in rust.
  • Add imm data APIs.
    • send_with_imm
    • receive_with_imm
    • write_with_imm
    • receive_write_imm

Optimizations and refactors

  • Redesign memory region. Use traits to describe three kinds of memory region abstraction. RawMemoryRegion records all information about the memory region Registered locally. LocalMr records information for local use. RemoteMr records information for remote use.
  • Discard preapplication of memroy region strategy. The old preapplication strategy is not flexible enough, so that is currently abandoned. And we will transform jemalloc to manage memory region and reuse it's preapplication strategy in the next release.
  • Change from dynamic generic to static generic.
  • Implement multi-task receiver. Just one task work with one ibv_recv_wr can not handle high-concurrency SEND requests. So more receiver tasks with more ibv_recv_wr were spawned to handle highly concurrent requests in this release.
  • Redesign memory region transfer APIs.
    • Refine the interface capability
      • Change from send_mr to send_local_mr and send_remote_mr.
      • Change from receive_mr to receive_local_mr and receive_remote_mr.
    • Take the ownership of the sent memory region. Prevent both ends from operating on the same memory region at the same time.

Bug fixes

  • Fix retry bug. When rnr_retry==7, the sender will keep retrying until the system freezes. We can't get any effective information to debug it because this part of the work is performed by the kernel module and there is no error message. But that will deplete CPU resources and the only thing we can observe is the system freezes. Solution is to make rnr_retry < 7.
  • Add timeout mechanism for remote requet operations to prevent Infinite wait.
  • Make Agent hold AgentThread to prevent the senders' release.

0.1.0

What is it and why make it?

Async-rdma is a framework for writing RDMA applications with high-level abstraction and asynchronous APIs.

Remote Direct Memory Access(RDMA) is direct access of memory from memory of one machine to the memory of another. It helps in boosting the performance of applications that need low latency and high throughput as it supports kernel bypass and zero copy while not involving CPU.

However, writing RDMA applications with low-level c library is laborious and error-prone. We want easy-to-use APIs that hide the complexity of the underlying RDMA operations, so we developed async-rdma. With the help of async-rdma, most RDMA operations can be completed by writing only one line of code.

What does it provide?

  • Tools for establishing connections with rdma endpoints.

  • High-level async APIs for data transmission between endpoints.

  • High-level APIs for rdma memory region management.

  • A framework working behind APIs for memory region management and executing rdma requests asynchronously.

Note

We develop async-rdma with the aim of becoming production-grade. But now it is too young, still in the experimental stage. We are adding more features and improving stability. We welcome everyone to try, ask questions and make suggestions.

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